1. Field of the Invention
This invention relates generally to the art of rolling and drawing, and more particularly to methods of straightening wire and machines for carrying out such methods.
The invention can find application in the production of metal cords, and flywire leads in electronic and electric-power engineering, as well as for making capillary tubes in microtechnology.
2. Description of the Prior Art
Advancements in wire straightening techniques and associated equipment has as the primary aim improvements in the physical and mechanical characteristics (such as strength and hardness), and geometrical parameters (such as roundness, linearity, and surface roughness) of the wire products.
There is known a method of straightening a wire (cf., British Pat. No. 2,129,720; Int. Cl. B 21 F 11/15, B 21 F 7/00, published May 23, 1984) involving twisting the wire in two opposite directions and stretching the wire. According to one feature of the method, the wire or rod is first twisted in the opposite directions, and then stretched.
There is also known a wire straightening device (cf., the same British Pat. No. 2,129,720) for carrying out the method as described in that patent and comprises a means for reeling out the wire, a means for twisting and stretching the wire, and a means for taking up the wire. In that device the means for twisting and stretching the wire includes a die through which the wire is threaded, a toothed rack, a gear ring engageable with the rack and embracing the die, and two clamps arranged at the opposite sides of the die.
However, according to that method and device, the wire straightening operation is carried out periodically, by preliminarily locking in place the portion of the wire being straightened, which increases the tendency of the wire to break, and affects the quality of wire straightening.
In addition, one more disadvantage of the above method and device for strengthening the wire resides in that the periodic straightening may cause, at various wire lengths, non-uniform tension of the wire and result in poor quality of the straightened wire.
One more disadvantage of the above prior art method and device resides in build-up of torsional strain of the material of the wire as it is being twisted, resulting in formation of loops tending to break inadvertently and again affecting the quality of wire straightening.